The invention relates to a rack jack for hoisting, lowering and/or supporting containers, cabins, shelters, exchangeable superstructures or the like, with whose corner fittings pinlike engaging parts of two arms cooperate, presenting respectively two supporting rods of different length, disposed on the jack shaft at a distance from each other and associated with the upper and lower corner fittings respectively, whereby the engaging part for the upper corner fitting is adjustable axially parallel to the jack and transversely to the axis of the jack, and the engaging part for the lower corner fitting is disposed perpendicularly with reference to the jack axis.
Such rack jacks are known for example from German Gebrauchsmuster (Utility Model) Nos. 7,419,031 and 7,502,135. The shafts of these rack jacks are respectively provided at the upper and lower end with shackles to which the arms are detachably fixed by means of connecting bolts, so that after use of the jack they can be removed and separately stored. To adapt the rack jack to different container heights, it is also known that a plurality of fastening shackles can be provided for the upper arm on a jack shaft of suitable length. The disposition of these fastening shackles is fixed, i.e., bound to quite specific heights of containers etc. and, moreover, the setting up of these rack jacks requires a relatively long time and the disassembled arms are parts that can readily be lost and that require extra storage. Especially though, these known rack jacks are quite heavy, which makes them hard to handle. This is attributable to the fact that the jack shaft is relatively long and its cross section at the point of connection for the lower arm--because of the geometry of this member--must be relatively large, and this large cross section extends over the whole structural height of the jack shaft.